1. Field of the Invention
The present invention relates to mobile communications networks, and more particularly to a method for managing user equipment version information in a mobile communications network, and a mobile communications network, a network element, and user equipment implementing said method.
2. Description of the Related Art
A mobile communications system refers generally to any telecommunications system wherein the access point (typically wireless access) to the system may change when users are moving within the service area of the system. A typical mobile communications system is a Public Land Mobile Network (PLMN). The mobile communications network is often an access network providing a user with a wireless access to external networks, hosts, or services offered by specific service providers.
Mobile communication systems are developed continuously and one of the main objectives is to provide a possibility to use IP services through the mobile system. Correspondingly, an IP technology is being developed to cover the conventional services of mobile systems, such as telephony. These two technologies have been combined in a 3GPP AII-IP system. The UMTS (Universal Mobile Telecommunication System) is an example of a system based on the IP technology defined in the co-operation project of what are known as a third-generation mobile systems, 3GPP (3rd Generation Partnership Project). The 3GPP AII-IP system is a biplane system comprising an application layer providing services and a transport layer providing data transfer. At least in the beginning the GSM system (Global System for Mobile Communications) and especially the services of what is known as the GSM 2+phase, such as the GPRS (General Packet Radio Service), are utilized in the transport layer.
FIG. 1 shows a simplified UMTS architecture illustrating only the parts essential to the invention, although it is apparent to a person skilled in the art that a common mobile telephone system also comprises other well-known functions and structures, which need not be discussed in greater detail here. The main parts of the UMTS are: a core network (CN) 150, a UMTS terrestrial radio access network (UTRAN) 100, and a user equipment (UE) 170. The interface between the core network 150 and the UMTS terrestrial radio access network 100 is called the Iu interface, and the air interface between the UMTS terrestrial radio access network 100 and the user equipment 170 is called the Uu interface.
The UMTS terrestrial radio access network 100 consists of a set of radio network subsystems 110, 111 (also called radio access networks) connected to the core network 150 over the Iu-interface. Each RNS is responsible for the resources of its cells. A radio network subsystem (RNS) consists of a radio network controller (RNC), and a multiplicity of nodes B, logically corresponding to base stations of traditional cellular systems. The interface between two radio network subsystems RNSs is called the Iur interface. The interface between the radio network controllers and the nodes B is called the Iub interface.
The radio network controllers 111, 121 are the network nodes responsible for the control of the radio resources of the UMTS terrestrial radio access network 100. A radio network controller 111 interfaces the core network 150 and also terminates the RRC protocol (Radio Resource Control) that defines the messages and procedures between the mobile and the UMTS terrestrial radio access network 100. It logically corresponds to a base station controller in the GSM systems. On connections between the user equipment 170 and the UMTS terrestrial radio access network 100, one radio network controller 111 is a serving radio network controller. As shown in FIG. 1, radio network controller 111 is connected to two core network 150 nodes, a Mobile Services Switching Centre/Visitor Location Register (MSC/VLR) 151 and a Serving GPRS (General Packet Radio Service) Support Node (SGSN) 152. In some network topologies it is also possible that one radio network controller 111 is connected to one or more than two core network 150 nodes which may be of similar or different type. For example, a radio network controller 111 can basically be connected to several SGSNs.
The main function of node B 112 is to perform air interface layer 1 processing (channel coding and interleaving, rate adaptation, spreading, etc). It also performs some basic Radio Resource Management operations, such as the inner loop power control.
The core network 150 may be connected to external networks, which can either be Circuit Switched (CS) networks (e.g. PLMN, PSTN, ISDN) or Packet Switched (PS) networks (e.g. the Internet). The core network 150 typically comprises a Home Location Register (HLR), MSC/VLR, a Gateway MSC GMSC, a SGSN and a Gateway GPRS Support Node (GGSN). The core network 150 described herein is based on a second generation GSM/GPRS network. Other types of core networks 150, for example IS-41, typically comprise other network elements.
The user equipment 170 can be a simplified terminal for speech only or it can be a terminal for diverse services acting as a service platform and supporting the loading and execution of various functions related to the services. The user equipment 170 comprises actual mobile equipment (ME) 171 and a detachably connected identification card such as a User Service Identity Module (USIM) 172, also called a subscriber identity module. In this context, the user equipment generally refers to the entity formed by the subscriber identity module and the actual mobile equipment. The USIM is a smart card that substantially holds the subscriber identity, performs authentication algorithms, and stores authentication and encryption keys and other subscription information that is needed at the mobile station. The mobile equipment is a radio terminal used for radio communication over the Uu interface between the user equipment 170 and the UMTS terrestrial radio access network 100. The mobile equipment may be any equipment capable of communicating in a mobile communication system or a combination of several pieces of equipment, for instance a multimedia computer to which a card phone has been connected to provide a mobile connection.
When launching new systems, it can be anticipated that at least during the early phases some kind of inconsistency will appear between the functionality of different types of user equipment 170. However, due to the vast number of UMTS features, it is not possible to test all possible terminal and network feature combinations before releasing new products or product versions into use. Thus, even if the user equipment 170 is tested and type approved, problems may arise either directly or through some unwanted side effects in activation of at least some new network features.
In order to overcome this it has been agreed upon in connection with the standardization work that the specification will allow sending an information element from the core network 150 to the radio network controller to indicate the specific behavior related to the user equipment 170. This will allow the radio network controller to adopt an appropriate corrective action by adjusting the operation towards the specific user equipment, either proactively or as soon as a problem is identified.
In order to be able to map the appropriate corrective actions to the specific user equipment group, 3GPP has specified an information element Software Version number (IMEISV). Naturally any other indicator capable of associating the user equipment 170 to a defined functionality type is possible. Thus in this context the term user equipment version should be interpreted to refer to a user equipment functionality set that is essentially similar for a user equipment group, wherein the user equipment specific behavior to be applied from the network side can be determined based on the user equipment version of the user equipment. The specified IMEISV comprises elements as shown in FIG. 2:                Type Allocation Code (TAC) 20,8 digits. The Type Allocation Code (TAC) is issued by a central body.        Serial Number (SNR) 21 6 digits. SNR is an individual serial number that uniquely identifies each equipment within each TAC. Manufacturers shall allocate individual serial numbers (SNR) in a sequential order.        Software Version Number (SVN) 22, 2 digits. SVN identifies the software version number of the mobile equipment. The Software Version Number is allocated by the manufacturer.        
According to the current specifications (ETSI 3GPP TS 24.008 V5.6.0 (2002-12), Technical Specification, 3rd Generation Partnership Project, Technical Specification Group Core Network, Mobile radio interface Layer 3 specification, Core network protocols; Stage 3, Release 5, later referred to as 3GPP 24.008), the core network 150 has two ways to receive the IMEISV of the user equipment 170. The core network 150 may request it separately through an Identity Request procedure, or request it within the Authentication and Ciphering procedure, as specified in 3GPP 24.008.
However, a separate signaling message sequence for delivering the information on the user equipment version causes unnecessary delay to the procedures and load to the system. In poor radio conditions the effect will even increase due to retransmissions. Furthermore, added signaling potentially increases the call fail risk, and the connection setup times are likely to grow.
As an example of the related problem let us consider emergency call handling. When an emergency call is initiated with the user equipment 170 without the USIM 172, or the user equipment 170 is provided with USIM 172, but is not attached, the appropriate information on the user equipment version is not appropriately available to the network. In such a case the core network 150, essentially the MSC 151, should automatically assume that the mobile is at the most basic functionality level, and signal this to the UMTS terrestrial radio access network 100, essentially the radio network controller 111. Since the user equipment is likely to be of some other functionality level, in order for the radio network controller to be able to apply the correct specific behavior related to the user equipment, the MSC actually needs to request the full IMEISV from the user equipment as described in 3GPP 24.008. This creates an considerable amount of additional signaling and typically increases the delay of the critical processes.
In another example, when a USIM 172 is removed from a first mobile in a location area of the first MSC, and re-inserted into a second mobile that is powered up in a location area of a second MSC, the mobile performs a circuit switched location update where the IMEISV is not exchanged. The new MSC can retrieve the IMEISV from the old MSC through a defined signaling procedure, but in this case the retrieved information will relate to the first mobile and therefore be incorrect. For the network to be able to apply the correct specific behavior associated with that the user equipment 170, again a separate signaling sequence and the related delays are necessary for requesting the full IMEISV from the user equipment.